Tracking of a golf shot and/or the measurement of a number of parameters associated with a golf shot are performed for a variety of purposes. For example, a golfer may wish to track the golf shots taken at a driving range and/or determine various parameters associated with the golf shots in order to gauge his/her performance. In addition, the manufacturers of golf clubs and golf balls oftentimes desire to track golf shots and/or to measure a variety of parameters associated with the golf shots in order to determine the performance of a golf club or golf ball.
Launch monitors are available to monitor various parameters associated with a golf shot. These parameters include the launch angle, the backspin of the golf ball and, in some instances, the sidespin of the golf ball. With respect to a golf ball sitting upon a tee, backspin is measured about a horizontal axis extending through the center of the golf ball transverse to the downrange direction in which the golf ball is driven. Conversely, sidespin is the angular rotation of the ball about a vertical axis extending through the center of the golf ball. Based upon these parameters, the anticipated path of travel of the golf ball can be projected quite accurately, thereby permitting a golfer or the manufacturer of a golf club or golf ball to determine the relative merit of the golf shot.
In order to determine the backspin and the sidespin of a golf ball, at least two images of the golf ball must be captured and analyzed. These images must generally be captured in quick succession so that the golf ball will have had an opportunity to rotate only a fraction of a revolution, as a result of either the backspin or the sidespin. Although the sidespin is generally less than few hundred revolutions per minute or less, the backspin may be in the neighborhood of 5000 revolutions per minute. For shots with a wedge, however, the backspin may be 12000 revolutions per minute or greater. As such, the images must be captured with only an extremely small time lapse therebetween. Additionally, the images must be captured prior to the exit of the golf ball from the field of view of the camera and generally with at least some spacing or separation between the images of the golf ball. For example, conventional launch monitors may require that the images that are captured be separated by about 1 to 5 milliseconds. Moreover, the images generally require relatively high resolution in order to permit the backspin and sidespin to be determined with the desired precision. As a result of the relatively high resolution and the precise timing of the images, the cameras that are generally utilized for monitoring the launch of the golf ball are quite expensive and may cost $15,000 or more.
Even with expensive cameras, conventional launch monitors cannot detect the backspin and sidespin of a standard golf ball. Instead, the golf ball must be marked in a particular manner in order to facilitate the detection of the backspin and sidespin of the golf ball. For example, the golf balls may be marked with a circumferential stripe as well as an additional marking. This additional marking may include tick marks on the circumferential stripe on opposite sides of the golf ball or a second circumferential stripe positioned at an angle, such as 90°, relative to the other circumferential stripe. By analyzing the relative positions of the circumferential stripe(s) at the times at which the two images are captured, the backspin and sidespin of the golf ball may be determined. Alternatively, the golf balls may be marked with a predefined pattern of reflective or fluorescent spots which are visible in the resulting images. By analyzing the relative positions of these spots at the times at which the images are captured, the backspin and sidespin of the golf ball can also be determined. As will be apparent, the requirement that specially marked golf balls be utilized in measure the backspin and sidespin of a golf shot further complicate conventional tracking techniques.
Moreover, conventional launch monitors generally require substantial alignment and calibration routines in order to properly position the launch monitor with respect to a golf ball. As such, it generally takes a significant period of time and, at least in some instances, a skilled technician to align and calibrate the launch monitor prior to use. Accurate operation of these conventional launch monitors is their dependence upon the golf ball being positioned the same distance away from the camera during each golf shot; a requirement that is not always met.
As such, it would be desirable to develop an improved technique for monitoring the launch of a golf ball and for determining various parameters associated with the golf shot including the backspin and the sidespin in a manner that is less expensive than conventional techniques. In addition, it would be desirable to develop a launch monitor that could be readily positioned and calibrated with respect to a golf ball, preferably in an automated fashion, while still permitting some variation in the spacing between the golf ball and the camera without adversely affecting the accuracy with which the launch monitor determines various parameters associated with a golf shot.